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Readability: What are complex words and how are they determined?

Guðrún Unnur Gústafsdóttir avatar
By Guðrún Unnur Gústafsdóttir

A complex word is defined by the Siteimprove algorithm as a polysyllabic word, which is a word made up of more than three syllables. Siteimprove's algorithm for the Readability feature within Quality Assurance does the following when checking and determining if words are "complex".

  • First the algorithm checks whether the word is compound (a word that is made up of two or more other words, e.g. Dragonfly). If it is, the algorithm splits it up and checks both parts individually (e.g. dragon and fly). 
  • If a word has suffixes (e.g. -es, -ed, -ing, -ly) that does not add complexity to the word, it is not considered complex.
  • The algorithm does not check for slang/jargon or specific words as there is no way of doing this, even though the definition of a complex word says to do that.
  • After the checks mentioned above the algorithm counts syllables and declares it as complex if the word is polysyllabic.

The readability test that looks at complex words is Gunning Fog.

The tests that include polysyllabic words in their algorithm are: Flesch Kincaid Grade level/Reading Ease & SMOG

Polysyllabic words can always be viewed in the page report of individual pages, by clicking on the magnifying glass on the specific link. Expand the list of polysyllabic words found on the page by clicking on the plus sign (+).

screen shot of readability scires

Image of page report for readability testing

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